Conventionally, as automatic tracking apparatuses, the below-mentioned monitoring systems are known in the field. That is, while the monitoring systems are equipped with cameras having panning, tilting, and zooming functions (namely, PTZ functions), the monitoring systems perform automatic tracking operations in such a manner that objects invaded into predetermined areas are detected, and furthermore, the detected objects are zoomed up in order that the zoomed-up objects may be photographed with having proper dimensions thereof, so that the invaded objects may be grasped in more detail.
Generally speaking, in the above-described monitoring systems, zooming magnification of the cameras have been set to wide-angle sides under initial conditions in order to monitor wide areas. After the invaded objects have been detected, if the detected invaded objects are rapidly zoomed up in order to transfer the present operation conditions to the automatic tracking conditions, then deformation amounts of images are increased, and thus, operators may easily lose track of the invaded objects, while the invaded objects are being tracked by performing block matching operations, template matching operations, and the like. As a consequence, the invaded objects are zoomed at relatively low speeds in such a condition that adverse influences caused by enlarging and compressing images can be hardly given.
As the conventional automatic tracking apparatuses, one automatic tracking apparatus is known from a patent publication 1. This automatic tracking apparatus has been arranged by a first image memory, a second image memory, a demultiplexer, a correlation calculator, and a moving object sensing program. The correlation calculator is constructed of hardware, and predicts a motion vector among such images whose photographing times are different from each other, while these images have been stored in the image memories. The moving object sensing program controls the correlation calculator in order to sense whether or not a moving object is present within an image photographed by a camera. Concretely speaking, the image is divided into a plurality of blocks, and then, a motion vector is calculated every block by the correlation calculator. The moving object sensing program traces the calculated vector so as to discriminate motion of a person from such a disturbance as swinging of a tree. When the moving object sensing program discriminates the motion of the person from the disturbance, the below-mentioned fact is utilized: That is, motion vectors such as persons may appear with having substantially same dimensions along a constant direction, whereas motion such as swinging of trees is produced in vibrating manners, so that motion vectors thereof do not continuously appear along the constant direction. Then, in such a case that motion vectors have been detected in a cluster shape, the moving object sensing program commences a tracking operation.
In the case that the camera itself performs a panning operation and a tilting operation, the automatic tracking apparatus extracts background motion vectors indicative of motion of the camera itself, and subtracts the background motion vectors from the vectors of the respective blocks, and thus, extracts motion vectors of an object so as to track the object. When a zooming operation is carried out during the tracking operation of the object, the automatic tracking apparatus predicts a change amount of enlarging an image and a change amount of compressing the image from the motion vectors, and predicts a motion vector of the object by subtracting the predicted change amounts from the vectors of the respective blocks so as to reduce adverse influences caused by the zooming operation, which are given to the tracking operation.
Another conventional automatic tracking apparatus is known from a patent publication 2. In order to solve the below-mentioned problem, this automatic tracking apparatus enlarges and compresses an area of a moving object extracted from imaging data based upon a plurality of arbitrary magnification so as to form a plurality of template images. In the above-described problem, in such a case that the moving object is enlarged and compressed by zooming this moving object, a dimension of a template image is not made coincident with a dimension of the moving object contained in the photograph data, so that the moving object cannot be tracked. When the moving object is enlarged and compressed by zooming this moving object, such template matching operations are carried out by employing template images of enlargement ratios and compression ratios, which correspond to dimensions of the enlarged images and dimensions of the compressed images, and thus, the moving object is tracked while considering correlation between these template images and the moving object.    Patent Publication 1: JP-A-2000-322581    Patent publication 2: JP-A-2001-243476